The BGS Lexicon of Named Rock Units — Result Details

Loch Laggan Psammite Formation

Computer Code: LLGN Preferred Map Code: LL
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Predominantly micaceous and feldspathic psammite with thin semipelite beds; turbiditic features. Abundant calc-silicate rock lenses and bands. Transitional upper and lower contacts.
Definition of Lower Boundary: Transitional with underlying Coire nan Laogh Semipelite. Base marked by lowest thick (10 m +) grey psammite.
Definition of Upper Boundary: Transitional into overlying Ardair Semipelite - progressive increase in mica content.
Thickness: variable 1.5 - 3.5 km
Geographical Limits: Central and southern Monadhliath Mountains, from Glen Roy to Strath Nairn and eastwards to Aviemore (Speyside).
Parent Unit: Corrieyairack Subgroup (GRCO)
Previous Name(s): Glen Doe Psammite Formation (GDOE)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Loch Lagganside to Glenshirra. Base on south side of upper Spey valley in Coire Bhein. Top on road cuts and sections above Moyonlaggan side. 
Reference Section  South-western flank of Beinn Sgurrach down from top to River Fechlin. 
Reference Section  Shoreside exposures north side of Loch Laggan around Rubha na Magach. 
Reference(s):
Key, R M, Clark, G C, May, F, Phillips, E R, Chacksfield, B C and Peacock, J D, 1997. Geology of the Glen Roy district. Memoir of the British Geological Survey, Sheet 63W [Scotland]. 
May, F and Highton, A J, 1997. Geology of the Invermoriston district. Memoir of the British Geological Survey, sheet 73W [Scotland]. 
British Geological Survey, 1995. Glen Roy, Scotland sheet 63W. Solid Geology 1:50000 (Keyworth, Nottingham, British Geological Survey). 
British Geological Survey, 1996. Foyers Scotland Sheet 73E. Solid geology 1:50000 [Keyworth, Nottingham, British Geological Survey]. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S074 S074 S064 S064 S063 S063 S073 S073